From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Grant Likely <grant.likely@linaro.org>,
Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
Jason Cooper <jason@lakedaemon.net>,
devicetree@vger.kernel.org, Laura Abbott <lauraa@codeaurora.org>,
keescook@chromium.org, linux-kernel@vger.kernel.org,
Rob Herring <robh+dt@kernel.org>,
Kumar Gala <galak@codeaurora.org>
Subject: Re: [RFC/PATCH 0/3] Add devicetree scanning for randomness
Date: Mon, 17 Feb 2014 17:13:07 +0100 [thread overview]
Message-ID: <1418981.0py7JxXCp8@wuerfel> (raw)
In-Reply-To: <20140217155419.682F7C401D4@trevor.secretlab.ca>
On Monday 17 February 2014 15:54:19 Grant Likely wrote:
> On Wed, 12 Feb 2014 11:20:00 -0700, Jason Gunthorpe <jgunthorpe@obsidianresearch.com> wrote:
> > On Wed, Feb 12, 2014 at 12:45:54PM -0500, Jason Cooper wrote:
> >
> > > The bootloader would then load this file into ram, and pass the
> > > address/size to the kernel either via dt, or commandline. kaslr (run in
> > > the decompressor) would consume some of this randomness, and then
> > > random.c would consume the rest in a non-crediting initialization.
> >
> > Sure is a neat idea, but I think in general it would probably be smart
> > to include the entire FDT blob in the early random pool, that way you
> > get MACs and other machine unique data too.
>
> I applied a patch that did exactly that (109b623629), and then reverted
> it (b920ecc82) shortly thereafter because add_device_randomness() is
> a rather slow function and FDTs can get large. I'd like to see someone
> do a reasonable analysis on the cost of using an FDT for randomness
> before I reapply a patch doing something similar. An awful lot of the
> FDT data is not very random, but there are certainly portions of it that
> are appropriate for the random pool.
Could we use a faster hash function that scans the entire device tree and
then just feed the output of that into add_device_randomness? We probably
can't expect that there is a lot of entropy in the DT blob, so the
result wouldn't be all that different in terms of quality of the random
seed.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: devicetree@vger.kernel.org, Laura Abbott <lauraa@codeaurora.org>,
Jason Cooper <jason@lakedaemon.net>,
linux-kernel@vger.kernel.org,
Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
Rob Herring <robh+dt@kernel.org>,
Kumar Gala <galak@codeaurora.org>,
Grant Likely <grant.likely@linaro.org>,
keescook@chromium.org
Subject: Re: [RFC/PATCH 0/3] Add devicetree scanning for randomness
Date: Mon, 17 Feb 2014 17:13:07 +0100 [thread overview]
Message-ID: <1418981.0py7JxXCp8@wuerfel> (raw)
In-Reply-To: <20140217155419.682F7C401D4@trevor.secretlab.ca>
On Monday 17 February 2014 15:54:19 Grant Likely wrote:
> On Wed, 12 Feb 2014 11:20:00 -0700, Jason Gunthorpe <jgunthorpe@obsidianresearch.com> wrote:
> > On Wed, Feb 12, 2014 at 12:45:54PM -0500, Jason Cooper wrote:
> >
> > > The bootloader would then load this file into ram, and pass the
> > > address/size to the kernel either via dt, or commandline. kaslr (run in
> > > the decompressor) would consume some of this randomness, and then
> > > random.c would consume the rest in a non-crediting initialization.
> >
> > Sure is a neat idea, but I think in general it would probably be smart
> > to include the entire FDT blob in the early random pool, that way you
> > get MACs and other machine unique data too.
>
> I applied a patch that did exactly that (109b623629), and then reverted
> it (b920ecc82) shortly thereafter because add_device_randomness() is
> a rather slow function and FDTs can get large. I'd like to see someone
> do a reasonable analysis on the cost of using an FDT for randomness
> before I reapply a patch doing something similar. An awful lot of the
> FDT data is not very random, but there are certainly portions of it that
> are appropriate for the random pool.
Could we use a faster hash function that scans the entire device tree and
then just feed the output of that into add_device_randomness? We probably
can't expect that there is a lot of entropy in the DT blob, so the
result wouldn't be all that different in terms of quality of the random
seed.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC/PATCH 0/3] Add devicetree scanning for randomness
Date: Mon, 17 Feb 2014 17:13:07 +0100 [thread overview]
Message-ID: <1418981.0py7JxXCp8@wuerfel> (raw)
In-Reply-To: <20140217155419.682F7C401D4@trevor.secretlab.ca>
On Monday 17 February 2014 15:54:19 Grant Likely wrote:
> On Wed, 12 Feb 2014 11:20:00 -0700, Jason Gunthorpe <jgunthorpe@obsidianresearch.com> wrote:
> > On Wed, Feb 12, 2014 at 12:45:54PM -0500, Jason Cooper wrote:
> >
> > > The bootloader would then load this file into ram, and pass the
> > > address/size to the kernel either via dt, or commandline. kaslr (run in
> > > the decompressor) would consume some of this randomness, and then
> > > random.c would consume the rest in a non-crediting initialization.
> >
> > Sure is a neat idea, but I think in general it would probably be smart
> > to include the entire FDT blob in the early random pool, that way you
> > get MACs and other machine unique data too.
>
> I applied a patch that did exactly that (109b623629), and then reverted
> it (b920ecc82) shortly thereafter because add_device_randomness() is
> a rather slow function and FDTs can get large. I'd like to see someone
> do a reasonable analysis on the cost of using an FDT for randomness
> before I reapply a patch doing something similar. An awful lot of the
> FDT data is not very random, but there are certainly portions of it that
> are appropriate for the random pool.
Could we use a faster hash function that scans the entire device tree and
then just feed the output of that into add_device_randomness? We probably
can't expect that there is a lot of entropy in the DT blob, so the
result wouldn't be all that different in terms of quality of the random
seed.
Arnd
next prev parent reply other threads:[~2014-02-17 16:13 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-12 1:33 [RFC/PATCH 0/3] Add devicetree scanning for randomness Laura Abbott
2014-02-12 1:33 ` Laura Abbott
[not found] ` < 201402121251.06280.arnd@arndb.de>
2014-02-12 1:33 ` [RFC/PATCH 1/3] of: Add early randomness hooks Laura Abbott
2014-02-12 1:33 ` Laura Abbott
2014-02-12 16:47 ` Grant Likely
2014-02-12 16:47 ` Grant Likely
2014-02-12 16:47 ` Grant Likely
2014-02-12 1:33 ` [RFC/PATCH 2/3] arm: Add ARCH_WANT_OF_RANDOMNESS Laura Abbott
2014-02-12 1:33 ` Laura Abbott
2014-02-12 16:49 ` Grant Likely
2014-02-12 16:49 ` Grant Likely
2014-02-12 16:49 ` Grant Likely
2014-02-13 0:54 ` Laura Abbott
2014-02-13 0:54 ` Laura Abbott
2014-02-13 0:54 ` Laura Abbott
2014-02-12 1:33 ` [RFC/PATCH 3/3] init: Move stack canary initialization after setup_arch Laura Abbott
2014-02-12 1:33 ` Laura Abbott
2014-02-12 11:51 ` [RFC/PATCH 0/3] Add devicetree scanning for randomness Arnd Bergmann
2014-02-12 11:51 ` Arnd Bergmann
2014-02-12 11:51 ` Arnd Bergmann
2014-02-12 17:45 ` Jason Cooper
2014-02-12 17:45 ` Jason Cooper
2014-02-12 17:45 ` Jason Cooper
2014-02-12 18:13 ` Olof Johansson
2014-02-12 18:13 ` Olof Johansson
2014-02-12 18:13 ` Olof Johansson
2014-02-12 18:32 ` Jason Cooper
2014-02-12 18:32 ` Jason Cooper
2014-02-12 18:32 ` Jason Cooper
2014-02-12 18:17 ` Arnd Bergmann
2014-02-12 18:17 ` Arnd Bergmann
2014-02-12 18:17 ` Arnd Bergmann
2014-02-12 18:45 ` Jason Cooper
2014-02-12 18:45 ` Jason Cooper
2014-02-12 18:45 ` Jason Cooper
2014-02-12 19:12 ` Arnd Bergmann
2014-02-12 19:12 ` Arnd Bergmann
2014-02-12 19:43 ` Jason Cooper
2014-02-12 19:43 ` Jason Cooper
2014-02-12 23:55 ` Rob Herring
2014-02-12 23:55 ` Rob Herring
2014-02-12 23:55 ` Rob Herring
2014-02-12 18:20 ` Jason Gunthorpe
2014-02-12 18:20 ` Jason Gunthorpe
2014-02-12 18:20 ` Jason Gunthorpe
2014-02-12 18:51 ` Jason Cooper
2014-02-12 18:51 ` Jason Cooper
2014-02-12 18:51 ` Jason Cooper
2014-02-17 15:54 ` Grant Likely
2014-02-17 15:54 ` Grant Likely
2014-02-17 16:13 ` Arnd Bergmann [this message]
2014-02-17 16:13 ` Arnd Bergmann
2014-02-17 16:13 ` Arnd Bergmann
2014-02-17 18:23 ` Jason Cooper
2014-02-17 18:23 ` Jason Cooper
2014-02-17 21:07 ` Geert Uytterhoeven
2014-02-17 21:07 ` Geert Uytterhoeven
2014-02-17 21:07 ` Geert Uytterhoeven
2014-02-18 17:56 ` Jason Cooper
2014-02-18 17:56 ` Jason Cooper
2014-02-18 17:56 ` Jason Cooper
2014-02-18 9:39 ` Grant Likely
2014-02-18 9:39 ` Grant Likely
2014-02-18 9:39 ` Grant Likely
2014-02-18 18:19 ` Jason Gunthorpe
2014-02-18 18:19 ` Jason Gunthorpe
2014-02-12 21:35 ` Kees Cook
2014-02-12 21:35 ` Kees Cook
2014-02-12 21:35 ` Kees Cook
2014-02-13 0:06 ` Laura Abbott
2014-02-13 0:06 ` Laura Abbott
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